This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Trans fatty acids (TFA) are of particular significance as risk factors for coronary heart disease (CHD), the major cause of death in North America. TFA in the diet come primarily from two sources, 1) industrial sources, partially hydrogenated vegetable oils (PHVO);2) natural sources, found in ruminant milk and meat, formed during the biohydrogenation of polyunsaturated fatty acids by rumen bacteria. Epidemiological data indicates that while adverse health effects are related to intake of TFA from industrial sources, this is not the case for TFA from natural sources. The isomer profile of TFA from industrial sources differs markedly from the profile found for TFA in natural sources, which we hypothesize leads to the reported differing effects on health. While studies have focused on lipoprotein profiles as a risk factor for CHD, atherosclerosis is characterized as a disease of chronic inflammation. Our studies will therefore provide data on the effect of TFA sources on lipoprotein profile, biomarkers of inflammation and actual atherosclerotic lesion development. This will provide important and currently-absent applied and mechanistic information regarding the impact of TFA sources on CHD and help inform government and health professionals in their development of policies and recommendations regarding health effects of TFA.